Ten years of experience in the rearing of young freshwater pearl mussels (Margaritifera margaritifera)
- 1.In rearing experiments performed between 1997 and 2007, captive-bred juvenile mussels were harvested shortly after they had dropped off their host fish, and exposed to different types of cages and holding systems.
- 2.Survival of juveniles ranged from 0 to 92% in the first 4 months, but the mean annual mortality was high in all trials and with all systems. In three trials with sheet cages and sediment boxes exposed to mussel rivers from an initial number of 1440 to 1660 only one to eight mussels reached 4 years of age.
- 3.With the exception of mussels kept in spring water no relationship between growth and survival was observed.
- 4.Low survival rates were obtained in sheet cages exposed to very oligotrophic and highly eutrophic brook stretches. Several natural sites that were lacking recruitment in the wild nevertheless showed good results in the cages.
- 5.All holding systems showed irregular variations in survival rates. Pairs of sheet cages showed no correlation between the survival of mussels in the adjacent cages. In contrast, growth rates were correlated.
- 6.No relationship could be found between the growth or survival in sheet cages at different sites and brooks and the corresponding data on water chemistry.
- 7.The systems tested for rearing young mussels involving a minimal time and effort in the natural habitat were not successful due to the elevated mortality rates of juveniles.
- 8.The rearing success of young pearl mussels in cages in the water flow of mussel rivers gives no information about the suitability of these sites for natural reproduction. Thus, to find potential natural habitats for Margaritifera, it is imperative to survey water quality, sediments and habitat structure. Copyright © 2010 John Wiley & Sons, Ltd.